Doctor plate



June 15,1926. 1,588,732

F. H. HOBERG DOCTOR PLATE Filed may" 25, 1923 INVENTOR.

ORNEYS Patented June 15,- 1926.

UNITED STATES 1,588,732 PATENT OFFICE.

rnnnx H. 30mm, or GREEN BAY, WISCONSIN.

.- DOCTOR PLATE.

Application filed May 23,

This invention relates to improvements in doctor'plates, i. e., in plates employed as take-off plates to remove moist'paper from a com ression roll to" which it tendsto adhere.

e objects of this invention are to provide means whereby the paper may be longitudinally crped to form stripes extending continuously from one end of the strip of paper to the other and each stripe having upset or displaced fibers characteristic of what is generally known as crpepaper, whereas the.

embodying my invention.

Figures 3 and 4 are sectional views drawn,

respectively, to lines 3-3 and 44 of Fig ure 2. a

Figure 5 is a longitudlnal section drawn to line 5'5'of Figure 2.

Figure 6 is a plan'view showing a modified form of doctor plate.

Figures. 7 and 8 are sectional views drawn, respectively, to lines 7-7 and 8-8 of Figlire 6.

Figure 9 is a fragmentary view on an enlarged scale showing the longitudinal creping or striping effect produced by my 1mproved doctor plate. I

Like parts'are identified by the same reference characters throughout the several views.

The paper pulp is fed upon an apron 1 and carried between it and a superposed apron 2 traveling at thesame speed. After the water has been "drawn out'of the pulp and the pulp compacted sufiiciently to form a continuous sheet of paper, the lower apron is run off around a roller .3 in such a manner as to leave the paper adhering to the upper apron, which is ordinarily composed of felt and which carries it between compression rollers 4 and 5. The 'paper tends 'to adhere to the roller 5, the felt apron assing upwardly around the roller 4 as indicated in Fig. 1. After the aper has thus been separated from the felt apron it is disen aged from the compression roller 5 by a octor plate latter being pivotally supported 1923. Serial No. 640,811.

from-the frame.8 by a bracket 9. \Vhen separated from the compression roller 5. by the doctor plate the paper passes over a series of idler rollers 10, 11, and 12 to the initial drying roller 13.

The parts above described may be of any ordinary construction, except as to the form of the-doctor plate, which is provided with a serrated edge margin 20 for contact with the compression roller 5. The apicefs 21 of the serrated margin are relatively high, being the terminals of longitudinally extending ribs 22. The reentrant angles 24 are at the bases of longitudinally extending grooves 25 formed in the surface of the doctor plate between the ribs 22. The ribs and grooves maybe formed by cutting parallel V-shaped grooves in the surface of the doctor plate and the serrated margin may be formed by beveling the working edge of the doctor plate from the opposite surface'toward the grooved surface as best shown at 26 in Fig. 5.

The beveled surface 26 bears upon the surface of the roller 5 and is either slightly concave in conformity with the surface of the .roller when first ap lied thereto or, if desired, it may be app ied with the points 21 in contact with the roller and allowed to wear until the entire beveled surface assumes a curvature corresponding with thatof the roller. The points 21 pass underneath the paper and lift it from the roller 5. These points engage the fibers of the paper with and also upset them with a tendency to form a rib in the paper. The portions of the paper between the points 21- of the doctor plate are lifted by the ribs 25 and kept out of contact with'the doctor plate, whereby these portions of the aper retain the appearance and texture imparted'to them by -1USt suflicient force to displace them slightly thecompression rolls. The paper is drawn therefrom to the upper surface of said it roller 10.

The bracket 9 is ivotally supported from -fthe frame at 30 an allows the doctor to swing by gravity into contact wit compression roller 5 and to, contra, a

take up wear by continuing to swing downwardly in proportion to the lessening dimensions of the plate.

While I have referred to the working edge of the doctor plate as having a serrated margin it will be understood from the above description of the preferred form of my invention that the serrations differ from ordinary serrations in that the sides of the notches extend obliquely downwardiy and rearwardly from the points. 21 to the bases of the grooves. The paper will be transversely crped or ribbedbetween the stripes only to the extent to which it is brought in contact with the converging end n'iargins of these notches. Those portions of the paper which are lifted by the ribs out of contact with the roller 5 before touching the doctor plate will not be crped but will retain the plain surface imparted to it by the compression rolls 4 and 5. The paper will, therefore, have longitudinally extending stripes a which will not be crped and the relative width. of these stripes will be determined by the pitch of the sides of the grooves which, in turn, determine the area of the paper which will contact with and be afiected by the action of the doctor plate. The form of the grooves in cross section will, of course, have some effect in determining the width of the stripe and the character of the 'erping action. But ordinary grooves V-shaped in cross-section will be found to give very satisfactory results, substantially as illustrated in Fig. 9.

In Figures 6, 7 and 8 I have illustrated a modified form of doctor plate in which the grooves 25 are formed on the under surface of the doctor plate, the upper surface being flat. The grooves have the form of an inverted V in cross-section and by beveling the working margin downwardly and outwardly from the edge 30, as indicated at 26*, it is obvious that the ribs will have chisel-shaped working ends, their edges 30 being chisel-shaped edges instead of pointed fingers as disclosed in Figures 2 to 6, inclusive. These chisel-shaped edges 30 are adapted to crepe the (paper transversely of each stripe, the stripe effect being obtained by having plain bands or stripes of less width than the plain bands or stripes a shown in Fig. 9. The notches or serrations in the working edge of this doctor plate will, of course, be much smaller than those of the plate shown in Figures 2 to 5, in-- portion of the plate at the working edge for action u on the paper, the efliciency or" the plate wil remain substantially unimpaired for a considerable period of time.

In referring to theapices 21 of the doctor plate shown in Figures 2, 3 and 4 as points, it is not intendedto imply that these are not chisel shaped. It is not essential that they should be either pointed like a'needle or edged like a chisel. The transverse dimension determines .to a considerable extent the .width of the crped stripe and the bluntness in the vertical dimension largely determines the degree of upset or displacement of the fibers.

I claim 1. A doctor plate for erping'paper and provided on one face with alternating ribs and grooves extending longitudinally across the plate,'the working margin of said plate being beveled transversely across said ribs and grooves and the ribs being tapered towards said workin margin to form a sawttiothed serrated edge transversely of said p ate.

2. A doctor plate for crping paper, provided on one face with alternating ribs and grooves and extending longitudinally across said plate, said plate having a beveled Working margin crossing the ribs and grooves and providing V-shaped recesses between the ribs and along the working margin.

FRANK H. HOBERG. 

